Key Takeaways

To be effective, treatment must address both conditions and involve a deep understanding of their connection.

Mood disorders, like depression, and substance abuse go together so frequently that doctors have coined a term for it: dual diagnosis. The link between these conditions is a two-way street. They feed each other. One problem will often make the other worse, according to the Anxiety and Depression Association of America (ADAA).

About 20 percent of Americans with an anxiety or mood disorder, such as depression, also have a substance abuse disorder, and about 20 percent of those with a substance abuse problem also have an anxiety or mood disorder, the ADAA reports.

Compared with the general population, people addicted to drugs are roughly twice as likely to have mood and anxiety disorders, and vice versa, according to the National Institute on Drug Abuse (NIDA).

The Shared Triggers of Depression and Substance Abuse

When it comes to substance abuse and depression, it isn't always clear which one came first, although depression may help predict first-time alcohol dependence, according to a study published in 2013 in the Journal of Clinical Psychiatry.

The brain. Similar parts of the brain are affected by both substance abuse and depression. For example, substance abuse affects brain areas that handle stress responses, and those same areas are affected by some mental disorders.

Genetics. Your DNA can make you more likely to develop a mental disorder or addiction, according to research published in 2012 in Disease Markers. Genetic factors also make it more likely that one condition will occur once the other has appeared, NIDA reports.

Developmental problems. Early drug use is known to harm brain development and make later mental illness more likely. The reverse also is true: Early mental health problems can increase the chances of later drug or alcohol abuse.

The Role of Environment

Environmental factors such as stress or trauma are known to prompt both depression and substance abuse.

These types of dual diagnosis may also be traced back to a time in early life when children are in a constant process of discovery and in search of gratification, according to David MacIsaac, PhD, a licensed psychologist in New York and New Jersey and president of the New York Institute for Psychoanalytic Self Psychology.

Any interruption or denial of this natural discovery process can manifest clinically and lead people to believe that everything they feel and think is wrong, he explains.

This idea, which Dr. MacIsaac says is based on the work of Crayton Rowe, author of the book Empathic Attunement: The 'Technique' of Psychoanalytic Self Psychology, challenges the idea that people dealing with depression try to self-medicate using drugs or alcohol. In fact, people with a dual diagnosis may be doing just the opposite, MacIsaac suggests.

"Individuals who are severely depressed drink to feed this negativity," he explains. "Initially it's soothing, but only for about 15 minutes. After that individuals sink deeper and deeper and feel worse than they did before."

For these people, MacIsaac points out, negativity is "where they get their oxygen." Any inclination that treatment is working will trigger a need to go back into the black hole of negative discovery, and alcohol will intensify their depression, he adds.

Why Simultaneous Treatment Is Important

Successful recovery involves treatment for both depression and substance abuse. If people are treated for only one condition, they are less likely to get well until they follow up with treatment for the other.

If they are told they need to abruptly stop drinking, however, depressed people with a substance abuse problem may be reluctant to undergo treatment, MacIsaac cautions. "They cling to drinking because they are terrified of losing that negativity," he says.